Hi-lo igniter



HI-LO IGNlTER Louis Lo Fiego and Robert K. Asplund, Newhall, and Rex L.Smith, China Lake, Califi, assignors, by mesne assignments, to theUnited States of America as represented by the Secretary of the NavyFiled Sept. 29, 1959, Ser. No. 843,327

2 Claims. (Cl. 10270) The present invention relates to igniters and moreparticularly to a novel igniter for propellant grains and the like.

The present invention comprises a circular container having a base, anda top member provided with a plurality of orifices. At least one squibis located on the inner side of the base member and a gas producingmaterial in intimate contact with the squib substantially fills thecontainer. When the squib is initiated and the gas producing materialis.ignited jets of flame are emitted from the orifices in the topmember. The present igniter provides improved ignition of solid rocketor missile propellants by improved control over the igniter reaction,particularly the high (gaseous) pressure phase of the reaction.

The previous and conventional methods of igniting solid rocket ormissile propellants employ thin, weak metal or plastic igniter casesprovided with blow-out plugs, discs or members which function atrelatively low and uncontrolled pressures, and also permit expulsion ofburning and unburnt portions of the igniter charge into the rocket motorchamber. The disadvantages of the previous igniters are lack of controlover igniter pressure; tendency to produce ignition shock; and, lack ofcontrol over direction and duration of the igniter flame. The presentinvention overcomes the disadvantages of prior art igniters byrestraining initial high igniter pressures within the igniter chamberand venting the igniter flame into a rocket motor chamber atsubstantially lower pressure. The present invention also preventsignition shock or initial high pressure peak in the rocket motorchamber; controls the rate of pressure rise in the motor chamber;increases the duration of the igniter flame; controls the direction ofthe igniter flame; reduces the amount of burning and unburnt ignitermaterial expelled into the rocket motor chamber; controls the reaction,and conserves space by eliminating the need for a small rocket sometimesused inside rocket motors for build-up to ignite propellant grain.

It is an object of the invention to provide a novel igniter forpropellant grains and the like.

Another object of the invention is to provide an igniter for improvedignition of solid rocket propellants and the like by improved controlover igniter reaction.

Another object of the invention is to provide a novel igniter forreducing ignition shock and preventing excessive expulsion of unburntigniter material into a rocket motor chamber.

A further object of the invention is to provide a novel igniter whichcontrols the direction and increases duration of the igniter flame.

Other objects and many of the attendant advantages of this inventionwill become readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

Fig. l is a cross-sectional, elevational view of a pre- 2,972,305Patented Feb. 21, 1961 ferred embodiment of an igniter of the presentinvention; Fig. 2 is a cross-sectional view taken along line 2-2 of Fig.1;

Fig. 3 is a perspective view of the embodiment of Figs. 1 and 2.

Referring now to the drawings like numerals refer to i like parts ineach of the figures.

Igniter 10 is constructed of a metal case 12 and closure portion 14containing igniter squibs 16 and igniter material 18. Case 12 is dishshaped and has recessed portions 20 in the base thereof in which squibs16 are seated and apertures 22 therethrough through which igniter squiblead wires 24 pass. One or more squibs 16 for initiating the ignitermaterial 18 may be used to suit particular desired conditions. The innerwall of case 12 may be threaded at 26 for holding closure portion 14 inplace. Closure portion 14 is threaded on the outer edge 28 thereof andhas a solid depending central portion 30 which seats in recess 32 in thebase of case 12. Closure 14 is provided wth a plurality of apertures 34through which igniter flame is vented into the propellant chamber of arocket motor. The number and size of apertures 34 control the pressureand rate of pressure rise.

The ring-shaped chamber 36 within the igniter case is filled withigniter material 18. The igniter material 1'8 may be a solid grain orpellets, Figs. 1 and 2 illustrate pellets as the igniter material. Alayer of cement 40 is provided between igniter material 18 and theapertured surface of closure portion 14 and protects the ignitermaterial 18 from the outside atmosphere- The casing may vary somewhat inassembly construction but preferably should have substantially the shapeas illustrated in the drawings.

The igniter case is constructed of metal of suflicient thickness andstrength to withstand pressures up to 10,000 p.s.i. without rupture andis provided with a predetermined number and size of vent holes whichpermit passage of the igniter flame to a rocket motor chamber at acontrolled pressure and rate of pressure rise. The igniter material 18in ignition chamber 36 when initiated by ignition elements or squibs 16creates highpressure igniter flame within the chamber. The igniter flamepressure is around 6,000 to 7,000 p.s.i. The initial high pressureresulting from initiation of the igniter charge within chamber 36 isconfined within the igniter case and flame passes to the propellantchamber of a rocket motor at a substantially reduced pressure, which aspreviously stated, is determined by the number and size of vent holes34. Since the device is a pressure vessel, enough vent holes 34 must beprovided to prevent bursting of the case. By providing a plurality ofsmall vent holes 34 the amount of incompletely burnt igniter material 18expelled from chamber 36 is greatly reduced, and the duration of theflame is increased. The vent holes also serve to control .the directionof the flame toward a rocket motor propellant grain. The direction ofsome of the vent holes may be varied slightly if it is desired to changethe direction of some of the flame jets.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

I. A propellant igniter for preventing initial high pressure peak andcontrolling the rate of pressure rise in a rocket motor chamber,comprising a container having an opening at one end and including abottom interior surface and a side interior surface, aclosure memberincluding a flat portion and a solid portion connected to and extendingin a right angle direction from the plane surface of said fiat portion,said flat portion having a plurality of orifices formed therein and theouter periphery thereof disposed in sealing engagement with saidopening, the extended'portion of said solid cylinder extending into saidchamber and spaced from said side interior surface and in fixed sealingengagement with said bottom interior surface thereby forming an annularspace between said solid portion, said side interior surface, saidbottom in terior surface and said flat portion having a plurality oforifices, said annular space being substantially filled with a gasproducing material, means positioned on said bottom interior surfaceoperable for initiating said gas producing material.

2. A propellant igniter for igniting the solid propellant of a rocketmotor, comprising a hollow cylinder having a solid closure at one endand an outlet closure at the other end, a solid cylindrical memberconcentrically disposedwithin said hollow cylinder and insealing'engagement with said solid closure and said outlet closurethereby forming an annular chamber, said chamber being filled with a gasproducing material, a plurality of means positioned on said solidclosure and adjacent said gas producing material for initiating said gasproducing material, said outlet closureyhaving a plurality of orificesdisposed in the section thereof adjacent said annular chamber.

References Cited in the file of this patent UNITED STATES PATENTS2,434,652 Hickman Jan. 20, 1948 2,462,305 Catlin Feb. 22, 1949 2,561,670Miller July 24, 1951 2,685,837 Sage Aug. 10, 1954 2,696,191 Sheehan Dec,7, 1954 2,848,872 Proell Aug. 26, 1958 2,872,870 Gey Feb. 10, 1959

